1. Field of the Invention
This invention relates to coaxial cable taps, and, in particular, to a method of installing a tap into a coaxial cable without having to sever the coaxial cable, and a coaxial cable tap assembly suitable for use in the installation method.
2. Introduction to the Invention
Coaxial cable is widely used in the communication industry to distribute television (TV) and other signals. This cable typically comprises: an inner conductor along which signals are transmitted; a dielectric surrounding the inner conductor; a rigid outer conductor cylinder which typically provides grounding and shields the signals from leakage and interference; and, optionally, a protective insulating outer jacket. For descriptive purposes, electrical signals and power are described herein as being transmitted on the inner conductor. However, while it is the pair of the inner and outer conductors together which carry signals and power, with the outer conductor typically grounded, the inner conductor may be thought of as carrying the electrical signals and power.
As used herein, a "tap" is a means by which a signal and/or electrical power can be extracted from and/or injected into a coaxial distribution cable. A tap may be used to pass signals, for example: between a distribution cable and a drop cable which leads to a subscriber's premises, referred to herein as a "drop tap"; between a first distribution cable and a second distribution cable, referred to herein as a "branch tap"; from a first point on a distribution cable to a second point on the same distribution cable, referred to herein as a "bypass tap"; or between a distribution cable and an apparatus capable of transmitting and/or receiving signals to/from a subscriber's premises via wireless communication, referred to herein as a "wireless tap". Modifications or combinations of the above may also be used. For example, a drop tap may be used to: extract power from a cable; combine the extracted power with a signal input to the drop tap from another tap; and output the combined power and signal to a subscriber via a drop cable. As used herein, a "tap assembly" is a device which is connected to a coaxial distribution cable to form a tap in the cable.
Coaxial distribution cables may carry electrical power in addition to a communication signal. Electrical power carried by the coaxial distribution cable may be used to power equipment located along the distribution system, including for example, amplifiers, line extenders, active taps and the like. In cable systems which carry telephone signals, electric power carried by the coaxial distribution cable may be used to provide power to telephones at subscribers' premises. The method and tap assembly of the invention may be used to pass electrical power, alone or in addition to signals, typically in drop taps and branch taps.
The known procedure for installing a tap into a coaxial cable is time consuming and labor intensive, and, when a tap is being added to an operating cable TV system, interrupts service. Thus, the coaxial cable is severed, both free ends of the severed coaxial cable are prepared with a coring tool, a connector is installed on each of the two prepared ends, and a tap assembly is inserted between the two connectors. In order to accommodate environmental stresses, a length of the coaxial cable surrounding the tap must be formed into an expansion loop. The tap assembly typically provides connections for subscriber drops.
It is common practice to interrupt cable television service downstream of the point where a tap is being added to an operating distribution cable. Moreover, when adding a tap to an operating distribution cable which is carrying both signal and power, special precaution must be taken to avoid injuring the craftsperson and/or equipment by exposure to the "live" power conductor.
Therefore, so that cable companies may expand to provide, for example, telephone or other services requiring uninterrupted operation, and/or services or equipment requiring electrical power to be carried on distribution cables, it is necessary that taps be capable of being made without interrupting the signal or power passing on the cable, and without exposing personnel and equipment to harm from a live conductor.